A caravan of some 1,200 Central Americans now trekking through Mexico, most of them Hondurans bound for U.S. ports of entry, has already begun to change the immigration debate in America.

Organized by a left-wing group called Pueblos Sin Fronteras, or People Without Borders, the stunt is brazen and reckless enough that it might just force U.S. policymakers to reevaluate America’s long-standing—and obviously failed—policy of strategic neglect toward Mexico and Central America.

According to a report by BuzzFeed on Friday, the caravan marched unopposed into Mexico from Guatemala last week, and since then “have boldly crossed immigration checkpoints, military bases, and police in a desperate, sometimes chaotic march toward the United States. Despite their being in Mexico without authorization, no one has made any effort to stop them.”

This presents the Trump administration with a unique challenge, especially if Mexico stands aside and allows the caravan to reach the U.S.-Mexico border. Mexico has a long history of failing to exercise sovereignty within its own territory, and the United States has a corresponding history, mostly forgotten today, of cross-border intervention when American interests were at stake.

If Mexican authorities prove unable or unwilling to stop the migrant caravan, President Trump could make the case that America has a compelling national interest in ensuring such caravans don’t reach the U.S. border, and that drastic measures, or the credible threat of such measures, are entirely appropriate.

Of course, an incursion into Mexico by the U.S. military would be a huge risk and it’s therefore extremely unlikely. But the existence of the caravan nevertheless represents a unique opportunity to change the parameters of an otherwise stale immigration debate in the United States—to shift from talking about enforcement tactics (like a border wall) to the root cause of mass migration: the collapse of civil society in places like Honduras and parts of Mexico.

Trump Says DACA Deal Is Off the Table

In fact, Trump might be laying the groundwork for such a shift. He took to Twitter Sunday night to denounce “ridiculous” U.S. immigration laws, Mexico, Democrats, and an amnesty deal, which he says is now off the table.

DACA is dead because the Democrats didn’t care or act, and now everyone wants to get onto the DACA bandwagon… No longer works. Must build Wall and secure our borders with proper Border legislation. Democrats want No Borders, hence drugs and crime!

A number of media outlets were quick to point out that the Central Americans in the caravan are not eligible for President Obama’s Deferred Action for Child Arrivals (DACA) executive order, which is technically correct but misses the point.

Trump brought up DACA, which protects some foreign citizens who were illegally brought to the United States as children, to highlight the fact that Democrats were unwilling to strike any kind of DACA deal, balking at even modest reforms to the immigration system and funding for Trump’s border wall. Democrats’ unwillingness to compromise, argues Trump, is all the proof you need that they don’t really want to secure the border, that they’re fine with uncontrolled mass immigration, and that he shouldn’t be expected to compromise with them.

On Monday, Trump continued in this vein, urging Senate Republicans to use the “nuclear option” and abandon the legislative filibuster so they can pass tougher immigration laws. Later on Monday, the White House released a statement expounding on what Trump had referred to, in an earlier tweet, as “ridiculous liberal (Democrat) laws like Catch & Release.”

Citing the numbers of unaccompanied minors and trespassing families U.S. officials have released into the country with orders to appear before a judge, the statement explained how current law limits the government’s ability to return illegal migrants to their home countries. “In the absence of lasting solutions to the problems that riddle our immigration system,” it read, “we can only expect the flow of illegal immigration into our country to continue.”

The Caravan Could Trigger a Crisis

But what is a “lasting solution” to our immigration problems? It’s not a border wall, nor is it simply loosening the laws that govern deportations and asylum proceedings. When hundreds or thousands of migrants are willing to trek through Mexico in massive caravans and present themselves at U.S. ports of entry to claim asylum—knowing they won’t get asylum but will be released into the United States—then it’s time to stop talking about walls and start thinking about major policy shifts.

Make no mistake: if the caravan reaches the U.S. border, it will be a disaster on several levels. At the most basic level, it will be a humanitarian crisis. Depending on where groups of migrants decide to cross, food, water, and exposure will be an immediate problem. Vast stretches of the U.S.-Mexico border are sparsely populated and geographically harsh. Facilities to house and feed hundreds of families for more than a day or two simply do not exist along the border. Most of those who manage to cross into the United States would have to be released before long.

While Border Patrol is dealing with all that, drug cartels would no doubt take advantage of the situation. While I was on a reporting trip to the Rio Grande Valley last month, Border Patrol agents told me that when unaccompanied minors began showing up in large numbers in 2014, it swamped their resources and left vast stretches of the border un-monitored. Drug cartels sent over large groups of minors on purpose, they said, as a diversionary tactic. A group of 80 or 90 children and families surrendering to Border Patrol would tie up every agent in that area for the entire day, allowing smugglers to ferry drugs across an unguarded border with impunity.

All of this would in turn trigger a political crisis that very well might accrue to Trump’s advantage. In some ways, the caravan is the worst possible development for Democrats, who have painted themselves into a corner on immigration by betting the future of their party on a rigid form of identity politics. For much of the Democratic Party’s base, “border security” is tantamount to racism.

If it appears the caravan is going to reach the U.S.-Mexico border, will Democrats even express alarm? Will they offer platitudes about the rule of law? Or will they finally admit that what they really want are open borders, mass immigration, and amnesty?